JP3027015B2 - Inkjet pen regulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regulator for regulating the pressure in a reservoir of an ink-jet pen.

[0002]

BACKGROUND OF THE INVENTION Inkjet pens have become an established printing technique, generally including the controlled supply of ink drops from an ink reservoir to a printing surface.

[0003] One type of ink-jet printing, called drop-on-demand, uses a pen having a print head that ejects ink drops from an ink reservoir in response to a control signal. Drop-on-demand ink-jet pens generally utilize one of two mechanisms to eject ink drops. That is, the mechanism uses a thermal bubble or a piezoelectric compression wave.

The print head of a thermal bubble pen has a thin film resistor that is heated to rapidly vaporize a small portion of the ink. The rapid expansion of the ink vapor forces a small amount of ink through the printhead orifice.

A piezoelectric compression-wave pen responds to a control signal by rapidly compressing the ink volume in the printhead, thereby generating a compression wave that causes a drop of ink to pass through the orifice. Use

While conventional drop-on-demand printheads are useful for ejecting, or "pumping," ink drops from a pen reservoir, the printhead may be used when the printhead is not operating. No mechanism to prevent seepage from Therefore, in the drop-on-demand technique, the liquid in the ink fountain needs to be stored so as to apply a slight negative pressure to the ink fountain in order to prevent the ink from leaking from the pen when the print head is at rest. The term negative pressure as used herein means that the fluid pressure in the reservoir is lower than the atmospheric pressure around the reservoir. Increasing the negative pressure means that the liquid pressure in the ink reservoir becomes more negative with respect to the atmosphere.

[0007] The negative pressure in the ink reservoir must be large enough to prevent ink from leaking from the printhead. However, the negative pressure must not be so large that the pumping function of the printhead cannot exceed the negative pressure when ejecting ink drops.

[0008] The negative pressure of the ink reservoir of an ink-jet pen changes when the printhead is activated to eject ink drops. Without adjusting for this negative pressure increase, the ink jet pen will eventually fail because the printhead will not be able to exceed the increased negative pressure to eject ink drops.

[0009]

SUMMARY OF THE INVENTION The present invention provides a mechanism for adjusting the negative pressure in an ink reservoir of an ink-jet pen to maintain a negative pressure above a level sufficient to prevent ink leakage from the printhead. Is what you do. This mechanism also ensures that the vacuum is not so great as to cause printhead failure. The range of the negative pressure level at which ink leakage is prevented and the operation of the print head is guaranteed is hereinafter referred to as a negative pressure operation range.

The present invention provides, among other things, a regulator comprising a valve seat and an associated valve member. The valve seat is attached to the body of the ink reservoir of the ink-jet pen. The valve seat has a hole formed therethrough. In a preferred embodiment, the valve seat is mounted such that the aperture communicates with a vent formed in the ink reservoir body. The vents allow for ink reservoirs and ventilation of the atmosphere. The valve member is mounted near the valve seat for movement relative to the valve seat. The valve member moves to the closed position in close contact with the valve seat to close the hole (and thus the vent) and moves to the open position away from the valve seat to open the hole (and thus the vent). It is configured.

The valve member is forced to a closed position by a magnetic force between the valve seat and the valve member. The valve member is forcibly separated from the valve seat by the negative pressure of the ink reservoir acting on the inner surface of the valve member. The magnetic force between the valve seat and the valve member normally closes the vent by holding the valve member in the closed position, so that a sufficient negative pressure in the ink reservoir to prevent ink leakage from the print head. And are arranged so as to be secured.

The magnetic force between the valve seat and the valve member closes the valve member until the negative pressure in the ink reservoir rises to a level sufficient to exceed the magnetic force (eg, as a result of ink depletion due to operation of the printhead). Hold in position. In particular, the regulator is designed such that when the negative pressure rises above the negative pressure operating range, the valve member is pulled away from the valve seat by the negative pressure acting on the inner surface of the valve member. Actuation of the valve member from the valve seat allows air to flow into the ink reservoir of the inkjet pen. As air flows into the ink reservoir, the negative pressure in the ink reservoir falls within the operating range and the valve member returns to the closed position with a magnetic force exceeding the reduced negative pressure.

The strength and shape of the magnetic field and the size of the valve member and valve seat are designed so that the valve member moves to the open position the moment the negative pressure rises above the operating range. Accordingly, the present invention provides a regulator that can be adjusted to precisely adjust the negative pressure of the ink reservoir.

[0014] In another aspect of the invention, the valve member has an intrinsic spring force.
e) is made of a magnetized material. Therefore,
Both magnetic and spring forces are used to close the valve member. In another aspect of the invention, the valve member and the valve seat are made of an elastomeric material to ensure a seal when the valve member is closed against the valve seat.

In another aspect of the invention, the regulator includes a deformable sealing mechanism that surrounds the aperture and deforms between the valve seat and the valve member when the valve member is in the closed position. This deformable sealing mechanism guarantees a leak-proof around the hole.

In another aspect of the invention, the magnetic force is provided by an electromagnet. As a result, the negative pressure operating range can be changed by controlling the strength of the magnetic field generated by the electromagnet.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, the regulator 20 of the present invention includes
2 to control the negative pressure inside.

The ink-jet pen 24 has an ink reservoir 2
And a pen body 26 defining a second liquid volume. The pen body 26 further includes a vertical hole 2 that contacts the liquid volume of the ink reservoir.
8 is also formed. The bottom of the vertical hole 28 is a conventional drop
An on-demand print head 30 is provided. The print head 30 operates to eject ink from the vertical holes 28 in a known manner, and the vertical holes 28 are supplied with ink stored in the ink reservoir 22.

As described above, the conventional drop-on
The demand type print head does not include a mechanism for preventing ink from oozing out of the print head when the print head is at rest, that is, when the print head is not controlled to eject ink from the ink reservoir. Thus, a negative pressure is created in the ink reservoir 22 of the ink-jet pen to balance the ink pressure of the printhead 30 so that there is no leakage from the printhead. The negative pressure is preferably generated when the ink reservoir 22 is filled with ink. The minimum level of negative pressure required to prevent leakage depends on the structure of the ink reservoir 22 and the type of printhead 30 used. Generally, the minimum negative pressure required to prevent leakage is about -2.5 cm (water column).

When the print head 30 is activated and ejects ink droplets, the negative pressure in the ink reservoir 22 increases due to a decrease in the liquid volume caused by the ejected ink. The most widely used print head 30 has a negative pressure of about -10 cm.
Even if it rises to the level of (water column), the ejection of ink droplets can be continued. However, above the maximum negative pressure,
The inability to pump against such a large negative pressure renders the printhead 30 inoperable. As described above, the range of the negative pressure level in which the ink leakage is prevented and the print head 30 continues to operate is called a negative pressure operation range.

The present invention provides an adjusting device 20 for preventing the negative pressure of the ink reservoir from rising to a level higher than the negative pressure operating range.
It has. The regulator 20 is mounted near a vent 32 formed in the top 34 of the pen body 26. Vent 32 provides ventilation between ink reservoir 22 and the atmosphere surrounding pen 24. The regulator 20 basically has a valve seat 36 mounted near the vent 32 of the pen body 26.
And a valve member 38. In one embodiment, valve seat 3
6 comprises a ferromagnetic stainless steel flat strip clamped to the inner surface 40 of the pen top 34. Valve seat 36
Completely covers the vent 32. An annular hole 4 is provided in the valve seat 36.
2 are formed. Since the hole 42 is ventilated with the vent 32, air can pass through the vent 32 and the hole 42 into the ink reservoir 22.

The valve member 38 is a flat, substantially rectangular member. One end of the valve member 38 is fixed to the valve seat 36 by a reservoir 44 or the like. The preferred embodiment of the valve member 38 is formed from a flexible elastomeric material having a magnetic material embedded therein. Therefore, when there is no reaction force, the valve member 38
The valve member is moved to a closed position shown by a solid line in FIG.

When the valve member 38 is in the closed position, the valve seat 36
The hole 42 is disposed at a position where the hole 42 is completely covered. Further, because the valve member 38 is formed from an elastomeric material, the valve member 38 is pressed against the valve seat 36, thereby substantially sealing off and closing the bore 42.

It will be appreciated that the closed valve member 38 seals the ink reservoir 22 and can create a negative pressure within the ink reservoir to prevent ink leakage from the printhead 30 during pauses. If the negative pressure in ink reservoir 22 increases during steady-state operation of print head 30, valve member 38 will remain closed until the negative pressure reaches a level that exceeds the negative pressure operating range (eg, a -10 cm water column). When the negative pressure exceeds the maximum level, the force of the negative pressure acting on the inner surface 48 of the valve member 38 increases, exceeds the magnetic force between the valve member 38 and the valve seat 36, and the valve member 38 is moved to the position shown in FIG. To the open position indicated by the dotted line. For clarity, the displacement of the open valve member 38 relative to the valve seat 36 is greatly exaggerated in FIG.

When the valve member 38 is in the open position, air can flow into the ink reservoir 22 through the vent 32 and the hole 42. As the atmosphere moves into the reservoir, the negative pressure in the reservoir decreases. As a result, the inner surface 4 of the valve member
The negative pressure acting on 8 decreases to a level at which the magnetic force between the valve member 38 and the valve seat 36 exceeds the negative pressure again and closes the valve member 38.

It will be appreciated that the regulator 20 of the present invention is a relatively simple mechanism for regulating the negative pressure in the ink reservoir of the ink-jet pen. Furthermore, regulator 2
Due to the small size of the zeros, very little ink reservoir volume is required to house the regulator 20. Thus, the ink reservoir of the ink-jet pen can incorporate the regulator 20 with only a small reduction in pen volume efficiency.

With the regulator 20 of the present invention, very precise adjustment is possible so that the valve member 38 opens at any maximum negative pressure selected by the pen designer. Thus, regulator 20 can accommodate a wide range of ink reservoir sizes and printhead performance characteristics. Many mechanisms are available for regulating the regulator so that the regulator 20 opens at the selected negative pressure level. (For convenience, the force required to move the valve member 38 to the open position is referred to as the "opening force" of the adjusting device.) For example, to adjust the opening force of the regulator 20, the valve seat 3 may be used.
The diameter of the hole 42 in 6 can be changed. In this regard, the larger bore 42 reduces the valve seat area covered by the valve member 38, and thus reduces the magnetic force between the valve member 38 and the valve seat 36. As a result, the negative pressure required to repel the reduced magnetic force is reduced, and the opening force of the regulator 20 is reduced.

It should be noted that as the diameter of the hole 42 in the valve seat 36 increases, the area on the upper surface 50 of the valve member 38 where positive atmospheric pressure acts with the negative pressure to force the valve member 38 to open. Is more exposed.

Another approach to adjusting the opening force of the regulator 20 is to adjust the overall size of the valve member 38 to change the total area of overlap between the valve member 38 and the valve seat 36, thereby providing a greater overlap between the two members. At a desired level.

Since the valve member 38 is made of the above-mentioned elastomer material or a flexible material such as ferromagnetic stainless steel described later, the valve member 38 has an inherent spring force. The spring force acts to move the valve member to the closed position together with the magnetic force between the valve member 38 and the valve seat 36. Thus, when the size of the valve member 38 changes, the inherent spring force of the valve member changes, thereby changing the opening force of the adjusting device.

As another structure of the regulator of the present invention,
To generate sufficient force to close the valve member 38, is made of metal that is magnetized the valve member 38, the valve seat 36, it is also possible to configure the elastomeric material inside the ferromagnetic material is embedded that There will be.

In the preferred embodiment, the valve member 38 has been described as being magnetized and the valve seat made of a ferromagnetic material, particularly ferromagnetic stainless steel. However, in another embodiment, the valve seat 36 could be magnetized and the valve member 38 could be formed from a ferromagnetic material.

FIG. 3 shows another embodiment of the regulator mounted near the vent 132 for the ink reservoir. The valve seat 136 is formed from a ferromagnetic material such as ferromagnetic stainless steel (or an elastomeric material having a ferromagnetic material embedded therein), and the valve member 138 has an attached cylindrical magnetic slug 158. The remaining portion of valve member 138 can be formed from any suitable flexible material, such as plastic. The magnetic piece 158 is mounted such that the magnetic force between the magnetic piece 158 and the valve seat 136 is maximized around a hole 142 formed in the valve seat 136.

FIG. 4 illustrates yet another embodiment of a regulator formed in accordance with the present invention. In particular, valve seat 2
36 is formed of plastic or another non-ferromagnetic material, and the valve seat 23 surrounds a hole 242 formed in the valve seat.
6 of ferromagnetic material embedded in the inner surface 264 of
62 are provided. The valve member 138 is formed similarly to the valve member 138 described with reference to FIG. Accordingly, the magnetic piece 258 attached to the valve member 238 is magnetically attracted to the ferromagnetic annular body 262 embedded in the valve seat 236.

In the embodiment shown in FIG.
May be formed of a ferromagnetic material, and the annular body 262 may be magnetized. Further, both the magnetic strip 258 and the annulus 236 could generate the magnetic force required to force the valve member 238 into the closed position by magnetizing each pole appropriately. . In this regard, it should be noted that any embodiment of the present invention may be configured to magnetize both the valve member and the valve seat.

FIG. 5 shows that each time the valve member 338 is closed, the valve seat 3 is closed.
14 shows another embodiment of the present invention in which a deformable seal 366 is provided to seal a hole 342 formed in 36. In the embodiment shown in FIG. 5, the valve member 338 is formed from an elastomeric material, and the sealing member 366 comprises an annular projection on a portion of the valve member surface near the aperture 342. The sealing portion 366 is shaped to surround the hole 342 formed in the valve seat 336. When the valve member 338 is closed, the sealing portion 366 is closed.
Is deformed between the valve seat 336 and the valve member 338. Sealing part 3
The deformation of 66 prevents air from leaking into the ink reservoir 22 from the atmosphere when the valve member 338 is in the closed position. As another structure, the sealing mechanism 366 is
It could be attached to

As mentioned above, the valve seat or valve member can be magnetized. Magnetization can be performed by an electromagnet.
For example, the valve seat 336 of the regulator shown in FIG. 5 is formed from an elastomeric material and leads 370 exiting the valve seat.
And an embedded electromagnet having: Lead wire 37
0 passes through the pen body and is connected to a switchable power supply. Electromagnet 368 activates to pull ferromagnetic piece 358 attached to valve member 338. It will be appreciated that, as an alternative, an electromagnet can be attached to the valve member 338. By using the electromagnet 368,
A simple way to adjust the opening force of the regulator is obtained. In particular, by changing the current supplied to the electromagnet 368,
While the negative pressure in the ink reservoir remains within the negative pressure operation range, the magnetic force between the valve seat 336 and the valve member 338 can be adjusted to the magnetic force required to ensure that the valve member remains closed. .

In certain applications, the small pieces 358 are magnets (or the valve member 338 may be formed of a magnetic material). When the electromagnet is off, the small pieces are pulled by magnetic force, and when the electromagnet is on, The poles of the strip 358 can be oriented so as to be displaced from the valve seat. By adjusting the current of the electromagnet, the spring force in the valve member can be substantially counteracted and, if necessary, finely adjustable so that the regulator opens as a result of a slight increase in the negative pressure in the reservoir. .

The opening force of the regulator can be reliably controlled by combining the above-described valve seat of the electromagnet and the magnetic valve member with the conventional pressure sensor 369 (FIG. 5). In this regard, a sensor 369 is provided in the reservoir for continuously indicating the fluid pressure in the reservoir. The output of the sensor is sent to a conventional feedback control loop (not shown) to control the current supplied to the electromagnet and thus control the opening force in response to changes in negative pressure.

FIG. 6 shows another embodiment of the present invention, in which the valve member 438 of the regulator is spherical and the valve seat 436 has a spherical valve member 438 which moves into the hole 4
A groove 472 that closes 42 is provided. More specifically, the top 434 of the pen body includes a vent 432 that opens into a chamber 474 formed in the inner surface 450 of the ink sump 434. The valve seat 436 is basically the vent 43
An annular member attached to the joint between the second and the chamber 474. The valve seat 436 has a vent port 42 and a central port 442 that vents. The shape of the groove 472 formed in the valve seat 436 is an inverted truncated cone. The groove 472 communicates with the hole 442.

The spherical valve 438 includes a screw 47 extending across a chamber opening near the inner surface 450 of the ink sump 434.
0 is fixed in the chamber 474. The magnetic force between the valve seat 436 and the spherical valve member 438 causes the valve member 438 to
Inward, thereby sealing the hole 442. When the negative pressure in the ink reservoir rises above the maximum negative pressure level, the resultant of the negative pressure acts against the magnetic force and moves the valve member 438 slightly out of the groove 472 (dotted line in FIG. 6). Atmosphere can flow into the ink reservoir through holes 442 and grooves 472, thus reducing the negative pressure in the ink reservoir.

In the embodiment shown in FIG. 6, either the valve seat 436 or the valve member 438, or both, can be formed from an elastomeric material to facilitate sealing of the valve member 438 to the valve seat 436.

The regulator of the present invention can be used with any number of pen configurations, and its use is not limited to pens having printheads that vent directly to the ink reservoir. For example,
FIG. 7 shows an ink-jet pen 52 stored in a shrinkable bag 580 in which ink is stored in an ink reservoir 522.
4 illustrates a regulator 520 mounted for use in FIG. The outside of the bag is exposed to the atmosphere via a vent 532. In the bag 580, the ink in the bag 580 is filled with the vertical holes 52.
8 has an opening 584 attached near the vertical hole 528 by, for example, a mounting ring 585. In the vertical hole 528, a partition plate 582 extending between the opening 584 of the bag and the print head 530 is formed. The partition plate 582 has a hollow 5 directly above the print head 530.
86 is formed. Openings 588 allow ink to flow from the bag into cavity 586.

The regulator 520 functions to create a negative pressure in the cavity 586 so that ink in the cavity 586 does not leak from the idle print head 530. In this regard, regulator 520 may be formed according to any of the previously described embodiments, and includes valve seat 536 and valve member 538. However, it should be noted that in order to generate the opening force of the valve member 538, it is necessary to take into account the fluid pressure of the ink acting on the valve member (via the holes 542).

[0045]

As described above, by opening and closing the valve member, the negative pressure in the liquid container is always maintained at a desired pressure suitable for ejecting ink droplets, thereby enabling good ink ejection in the ink jet pen.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an inkjet pen including a regulator according to an embodiment of the present invention.

FIG. 2 is a view as seen from the arrow line 2-2 in FIG. 1;

FIG. 3 is a sectional view of a regulator according to another embodiment of the present invention.

FIG. 4 is a sectional view of a regulator according to another embodiment of the present invention.

FIG. 5 is a sectional view of a regulator according to still another embodiment of the present invention.

FIG. 6 is a sectional view of a regulator according to still another embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a case where the regulator of the present invention is used in another mode.

[Explanation of symbols]

 20: Regulator 22: Ink reservoir 24: Pen 26: Pen body 28: Vertical hole 32: Vent 36: Valve seat 38: Valve member 42: Hole 44: Stop fitting

Continuation of the front page (56) References JP-A-60-204359 (JP, A) JP-A-60-204356 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2 / 175 B41J 2/045 B41J 2/055

Claims (3)

(57) [Claims] 1. An ink reservoir having a vent and ink.
And a print head for ejecting ink
Adjust the pressure inside the ink reservoir of the ink pen
Regulator for Has a hole that communicates between the vent and the ink reservoir
A valve seat provided to cover the ventilation port, Attached to the valve seat operably to open and close the hole
Provided with a valve member, The valve seat and the valve member are magnetized so that a magnetic force acts between them.
Composed of a combination of conductive material and magnetized material,
The hole is urged in a direction to close the hole by magnetic force,
So that the pressure in the storage container maintains the desired pressure.
The valve member opens and closes, and further, By changing the opening area of the hole of the valve seat,
And / or changing the size of the valve member, and
By changing the contact area of the valve seat, the ink
The value of the desired pressure in the reservoir is changed.
A regulator characterized by that: 2. The valve member includes a flexible material,
A method of closing the hole by the inherent spring force in addition to the magnetic force
2. The device according to claim 1, wherein the device is biased in a direction.
Regulator. 3. The valve member and / or the valve seat according to claim 1,
The contact surface contains an elastomeric material and is
The method according to claim 1 or 2, wherein
regulator.